1. Field
Embodiments of the present invention relate to a disc brake, and more particularly, to a disc brake that may reliably return a piston when a braking operation is completed and improve a return effect.
2. Description of the Related Art
In general, a disc brake is a device that stops rotation of a disc by forcibly pressing a friction pad onto both surfaces of the disc that is rotated together with wheels of a vehicle, and thereby may brake the vehicle.
For such a disc brake, a method of retracting a piston using a sealing member and a roll-back chamfer in order to reduce a drag phenomenon in which the disc and the friction pad are continuously rubbed after the braking operation, and a method of forcibly retracting the piston together with a pad plate for pressing the disc by installing a pressure spring in the pad plate are used. However, when using the sealing member and the roll-back chamfer for a long time, durability of the sealing member is reduced so that retraction of the piston does not occur smoothly, and a drag phenomenon is generated by a back slip phenomenon. In addition, when using the pressure spring, a running clearance between the disc and the pad plate is increased by the abrasion of the friction pad mounted in the pad plate by forcibly returning the pad plate and the piston to its original position, and therefore a brake feeling is changed.
Thus, in recent years, a disc brake that reliably returns the piston to its original position while maintaining the running clearance between the disc and the pad plate even though the friction pad is worn has been proposed. In particular, in Korean Patent Publication No. 10-2013-0086438, a disc brake that can ensure a predetermined running clearance between the disc and the pad plate in an early stage of braking is disclosed. In the disclosed disc brake, an adjuster is provided to maintain the running clearance between the disc and the pad plate constant, and a low pressure spring that acts according to a low pressure and a high pressure spring that acts according to a high pressure are arranged in parallel for a smooth return of the piston and the pad plate to retract the piston, and thereby may prevent drag and ensure the running clearance between the disc and the pad plate.
However, there are problems that the volume of the disc brake is increased so as to ensure a mounting space for installing the two springs when the low pressure spring and the high pressure spring are arranged in parallel, and manufacturing costs are increased due to an increase in the number of parts.